A top United Nations official says rival factions vying for power in Libya have agreed in principle to hold a new round of peace talks in early January.

U.N. Libyan envoy Bernadino Leon told the 15-member Security Council that the long-delayed talks are set for January 5, and will focus on a cease-fire, a national unity government and a new constitution.

Libya was effectively left without governance after longtime dictator Moammar Gadhafi was overthrown in 2011.

Its internationally recognized government, led by Prime Minister Abdullah al-Thani, fled to the eastern city of Tobruk earlier this year, as an Islamist militia seized control of the nation's capital, Tripoli.

In a related development Tuesday, the U.N. High Commissioner for Human Rights, Zeid Raad al-Hussein, reported hundreds of Libyan deaths in areas where civilians remain trapped between rival forces.

The report described widespread shelling of some civilian areas, forcing at least 120,000 people from their homes between September and mid-December.

U.N. spokeswoman Ravina Shamdasani, speaking to reporters in Geneva, said "there is a serious lack of law and order" in the country and "absolutely no accountability." She said some of the violence "may amount to war crimes."